Concurrency |

When sync.Cond is a better primitive than channels: lessons from Go's HTTP/2 client

Sep 17, 2026 · 14 min read · Go Concurrency ·

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I recently reviewed code that let a dynamic set of goroutines wait for updates from a single writer. Each waiter wanted to block until the writer had published something newer than what it had already seen. The implementation used channels and was hard to follow. A condition variable (sync.Cond) would have been less …

Using WaitGroup to Track Work Items, Not Workers: A Multi-threaded BFS Example

Feb 15, 2026 · 5 min read · Go Concurrency ·

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WaitGroup and channels are two powerful primitives in Go for synchronizing goroutines. A common pattern uses a WaitGroup to wait for goroutines completion: 1wg.Add(1) 2go func() { 3 defer wg.Done() 4 for { 5 select { 6 case <- done: 7 return 8 case task <- tasks: 9 handle(task) 10 } 11 } 12}() 13wg.Wait() In this …

Sharp edges of errgroup: Lessons from an errgroup and Context mishap

Mar 23, 2025 · 8 min read · Go Concurrency ·

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A recent faulty release disrupted service for some customers. The root cause was a concurrency bug involving x/sync/errgroup and context cancellation. This post shares three practices we learned from the incident. These practices will help us catch similar issues during code review or alert us to problems in …

False sharing: a look at cache line and write combining

Feb 23, 2024 · 7 min read · Go Concurrency ·

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Modern CPUs operate significantly faster than memory. A 4.5 GHz x86_64 CPU operates 30 times faster than 6000 MHz DDR5 memory with CAS Latency 36. When accounting for latencies from the bus and memory coherency protocols, memory can be 100 times slower than registers. To mitigate this speed gap, CPUs use layers of …